Pseudomonas aeruginosa (P. aeruginosa) is a Gram-negative, aerobic, rod-shaped and polar-flagella bacterium with unipolar motility. Furthermore, it is an opportunistic pathogen responsible for ventilator-acquired pneumonia (VAP). VAP due to P. aeruginosa is usually multidrug-resistant and associated with severe infection and increased mortality. The goals of this review are as follows: (I) to present selected recent epidemiological literature characterizing the population at risk of P. aeruginosa pneumonia, (II) to describe some of the virulence factors of P. aeruginosa that are related to infection, and (III) to illustrate clinical outcomes of ventilated patients with large burdens of P. aeruginosa as well as the mechanism by which this bacterium may evade the host immune response.